1. Field of the Invention
This invention relates to improvements in stuffing glands and more particularly, but not by way of limitation, to a pressure balancing stuffing gland for shafts subjected to relatively high pressures.
2. Description of the Prior Art
In any pressure vessel having a shaft or stem protruding therefrom through a single opening, such as a gate valve stem, or the like, the shaft is urged axially outwardly from the vessel by a force in pounds equal to the projected area of the largest sealed diameter of the shaft (expressed in square inches) multiplied by the internal pressure in pounds per square inch, commonly known as psi. The pressure thus acting on the shaft causes difficulties in operation of the shaft, particularly when the internal pressure in the vessel or valve is relatively high. The force urging the shaft axially outwardly must be overcome in some manner in order to activate the shaft, such as to rotate the shaft about its longitudinal axis, as in order to open or close a gate valve. For example, a one inch diameter shaft extending or protruding from a vessel having an internal pressure of one thousand psi is urged outwardly by a force of seven hundred eighty pounds. A two inch diameter shaft subjected to the same pressure conditions is pushed by a force equal to 3,142 pounds. It will be readily apparent that powerful operators and/or high quality bearings must be utilized for overcoming these forces in order to actuate the shaft. The stuffing gland disclosed in my prior U.S. Pat. No. 4,240,675 is arranged for equalizing the pressures acting on the shaft for greatly reducing the force required for actuation of the shaft. The particular design of the shaft in my aforesaid patent requires a considerable amount of machining in the case of a long shaft, which is not only an expensive operation, but also results in considerable waste of material.